Hybrid electric vehicles (HEVs) use batteries as an energy storage system. The plug-in hybrid electric vehicle (PHEV) is an extension of existing hybrid electric vehicle (HEV) technology. A PHEV utilizes a larger capacity battery pack than a standard hybrid electric vehicle, and adds the capability to recharge the battery from a standard electrical outlet to decrease fuel consumption and to further improve the fuel economy in an electric driving mode or in a blended driving mode. There are also battery electric vehicle (BEV) applications where an electric machine completely replaces the internal combustion engine.
The HEV, PHEV, and BEV each include an electric motor drive system, which may include a permanent magnet (PM) synchronous motor. A PM synchronous motor includes a rotor having permanent magnets mounted on the rotor periphery or buried inside the rotor. The electric motor drive system generates torque ripples. The motor output torque contains torque ripples caused by the magnetic force variations depending on the rotor position of the motor.
In an existing approach to reducing torque ripple in interior permanent magnet (PM) machines, torque ripple is minimized via machine design.
Background information may be found in U.S. Pub. No. 2008/0246425A1 and in JP2009195049A.